'Time Stamp' in Brain Cells Encodes Memories

WEDNESDAY Jan. 28, 2009 -- The thousands of new brain cells generated each day in an adult's brain carry a code that "time stamps" memories, according to researchers at the Salk Institute for Biological Studies in California.

"By labeling contemporary events as similar, new neurons allow us to recall events from a certain period," study leader Fred H. Gage, a professor in the Laboratory for Genetics, said in an institute news release.

But this neuronal time code provides only relative time, not a precise time stamp like the type found on digital photographs, the researchers explained.

For this study, the Salk team developed a computer model designed to simulate the neuronal circuits in a part of the brain called the dentate gyrus, which spawns new brain cells in adult brains.

The dentate gyrus is the entryway to the hippocampus, which distributes memory to appropriate storage areas of the brain after it prepares the information for efficient recall.

The researchers found that newborn brain cells respond indiscriminately to incoming information. Eventually, these cells mature and take their place in the existing circuitry.

"Current thinking holds that when we bring up a certain memory, it passes back to the dentate gyrus, which pulls all related bits of information from their off-site storage. Our hypothesis suggests that cells that were easily excitable bystanders when the memory was formed are engaged as well, providing a hyperlink between all events that happened during their hyperactive youth," Gage said.